A known electrophotographic image forming apparatus includes a fuser including a heat roller, a pressure roller, a spring, and a cam. The pressure roller is configured to move between a nip position and a nip release position. At the nip position, the pressure roller is in pressured contact with the heat roller with the aid of the spring and the cam. At the nip release position, the pressure roller is separated from the heat roller.
The cam receives drive force from a drive source, via a plurality of gears. The drive force from the drive source causes the cam to rotate in a particular rotating direction (e.g., forward direction), thereby moving the pressure roller from the nip position to the nip release position against an urging force of the spring. Mating teeth of the gears located between the cam and the drive source have backlash.
When the pressure roller moves from the nip release position to the nip position, the cam may be applied with a moment to urge the rotation of the cam in the forward direction due to an urging force of the spring. The moment may cause the cam to rotate in the forward direction at a higher rotating speed (what is called “forward slip”) than its regular rotating speed of the cam. The backlash between the mating teeth of the gears may cause noises during the forward slip of the cam.
The fuser includes a braking mechanism configured to brake the faster rotation of the cam caused by the urging force of the spring, thereby preventing or reducing noises attributable to backlash. The braking mechanism includes a partial gear having a missing gear section on a peripheral portion of the partial gear, and a full gear having gear teeth on an entire peripheral portion of the full gear. The partial gear is configured to rotate together with the cam. The full gear is connected to a torque limiter. When the pressure roller is moved from the nip release position to the nip position, the partial gear engages the full gear. The force of the torque limiter may brake or slow the faster rotation of the cam caused by the urging force of the spring.